A series of experiments are proposed to study the development of cardiovascular activity in the newborn spontaneously hypertensive rat. Comparisons will be made between the SHR and the normotensive parent strain, the Wistar Kyoto rat (WKY), regarding their relative cardiovascular responsiveness from birth through adolescence. During the neonatal period repeated measurements of heart rate will be made while the rats are in a resting state and while they are responding to cold stress, mild electric shock, and anesthesia. Following weaning, heart rate (and possibly blood pressure) will be recorded during an appetitive conditioning task and, later, during an aversive conditioning task. In this way, the autonomic activity of these genetically hypertensive and normotensive rats may be compared during quantifiable behavioral states motivated by reward and by punishment. Findings of this study regarding the ontogeny of abnormalities in cardiovascular activity in the SHR may help in the early detection of hypertension in man.